Hydroformylation of Higher Olefins Using Radium Phosphite Complex Catalyst

Hydroformylation of olefins with CO and Hz at total pressure of IS to 50 bar and
temperature of 80 to l20°C, in presence of rhodium (Rh)-based homogeneous catalysts
for production of aldehydes has demonstrated high yields and selectivity. Rh-based
catalysts are expensive and the commercial viability of a process that uses such catalysts
substantially depends on the efficiency of catalyst recovery and product separation. In
this work, a novel temperature dependent multi-component solvent (TMS) or
'thermomorphic solvent' system has been used as the reaction medium to investigate
hydroformylation of two higher olefins - 1-octene and 1-dodecene - to synthesize the
corresponding aldehydes at a lower pressure of 15-25 bar and temperature of 80 to
100°C. Such a solvent mixture changes thermally from biphasic to monophasic with
distribution of the products and of the catalyst in the non-polar and polar phases thus
simplifying the process of separation and recycling of the catalyst.
A TMS- system consisting of three components - propylene carbonate (PC), ndodecane
and 1,4-dioxane was used in this study. The presence of 1,4-dioxane imparts
the thermomorphic character to the solvent mixture. For a gas-liquid reaction, the
solubility of the reactant gas in the liquid medium is an important parameter required for
the interpretation of reaction kinetics. Therefore experimental measurement of solubility
of the gaseous reactants - CO and Hz - in the individual components of the solvent as
well as in their mixtures was performed up to a pressure of 1.5 MPa and temperature
range of 298-343 K. The effects of solvent composition, partial pressures of the gaseous
reactants - CO and Hz, reaction temperature and catalyst loading on the rate, yield and
selectivity of the linear aldehydes were also investigated. At a reaction temperature of
363 K and total pressure of 1.5 MPa and 0.68 mM HRh(CO)(PPh3)3, the conversion of 1-
octene and the yield of aldehyde were 97 % and 95 %, respectively. The aldehyde
product was recovered in the non polar phase whereas the catalyst remained in the polar
phase with low catalyst loss of 3 %. With a reaction-time of 2 h and a selectivity of 89 %,
this catalytic system can be considered as highly reactive and selective. The rate was
found to be first order with respect to catalyst, 1-octene and PH, . The rate vs. Pco
resembled a typical case of substrate inhibited kinetics.

Hydroformylation of Higher Olefins Using Radium Phosphite
Complex Catalyst